This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this research protocol is to prospectively evaluate the natural history of nonalcoholic fatty liver disease. Nonalcoholic steatohepatitis (NASH) is defined by a liver biopsy and consumption of alcohol in amounts less than those likely to produce liver injury. NASH and a fatty liver disease (fat accumulation in the liver) represent the entire group of diseases commonly referred to as nonalcoholic fatty liver disease (NAFLD). This condition is also associated with obesity and diabetes. NAFLD can lead to progressive liver injury with the accumulation of scar tissue in the liver (fibrosis), which can in some cases, lead to cirrhosis. It is currently unknown why some people develop advanced liver disease and what fraction of the patients with NAFLD develop fibrosis in the liver. Furthermore there is no established treatment of NAFLD, and previous studies of NAFLD fail to study the liver tissue during disease progression. The primary objective of this study is to determine 1) what proportion of subjects with NAFLD develop increasing amounts of scar tissue in the liver, 2) the rate at which the scar tissue develops in the liver, 3) the factors that determine why some people develop scar tissue more rapidly than others. Secondly, this study proposes to analyze the underlying psychological and social factors that determine why some patients can adhere to the diet proposed in the treatment of NAFLD and some have much more trouble. Standard physician visits and routine bloodwork in the treatment of liver disease will continue. The research tests and procedures that are additional to the standard of care will be done in accordance with these standard visits. In order to be eligible for participation in this study, a questionnaire must be completed to determine if the use of alcohol is a contributing factor to the liver disease, only patients who do not use alcohol and have clear documentation of fatty liver disease will participate. Upon enrollment into the study, participants will have an oral glucose tolerance test to rule out the presence of diabetes, a detailed nutritional assessment, and a complete a series of physchological questionnaires. Participants will be followed for ten years with continuing nutritional, physical, and physchological data being gathered at specified intervals.